Carburetor



July 24, 1934. A M PRENTlss 1,967,423k

v -CAHBURETOR Filed Feb. l. 1952 W4@ QQZSM ATTORNEY temperature control of the acceleration fuel sup- Whieh liquid fuel under SupeletmOSDlleriC PreS- increase the acceleration of the engine. SeCOnd air passage 20 Whieh in turn communithe carburetor so that, as this temperature inof the carburetor by means 0f a metering restric- Patented July .24, 1934 t CARBURETOR Augustin M. Prentiss, San Antonio, Tex., assgnor to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware-v Application February 1, 1932, Serial No. 590,293

17 Claims. (Cl. 5561-34) This invention pertains to carburetors and more and mixture outlet 5 controlled by a butterfly particularly -has reference. to temperature conthrottle valve 6. The term mixing chamber trolled acceleration devices for carburetors of the as used in this application does not include the pressure' feed type, portion of the passage which lies posterior to the .5 This invention is an improvement on the inventhrottle. Integral with the bottom wall of air o tion disclosed in my United states Patent 1,329,309, intake passage 2;.is a main iet nozzle 'l which rises issuedJanuary 27, 1920, and this application is a to a point just above the center of throat 3 and continuance in part of my copending application consists of an outer liquid fuel tube 8 and a con- Serial No. 520,292, filed February l, 1932. centric inner compressed air tube 9. Tube 8 10 In the pressure feed type of carburetor shown is surmounted by an adjustable screw-threaded inmy eopending application, serial No. 580,992, cap 10 having a central aperture 11 through which nied December 14, 1931, and serial No. 590,292, no the compressed air and liquid fuel issue in the special apparatus was provided for acceleration, ferm 0f a nely atemized Spray- It Will be appresole reliance being placed on the greatly superior ciated that the relative positions of the air and 15 performance secured by the use of a compressed liquid fuel tubes may be reversed Without appreair liquid fuel feed. I havefcund that, while the oiably affecting the functioning of nozzle 7 or deacceleration performance of the pressure feed parting frOnl the spirit Of my inVentiOn. Liquid carburetor greatly excels that of the convenfuel tube 8 communicates through a passageway tional vacuumfeed carburetor, there is a need for 12 and p0rt 13 With a liquid fuel reSerVOr 14 into ply,4 I have also found that even more rapid acsure enters through an inlet 15 controlled by a 5 celeration at lower temperatures can be secured ValVe 16 Which iS actuetted by a' float 17 t0 mainthrough a momentary augmentation of the ac.. tain the liquid fuel at a normal level X-X in the celeration fuel supply even in pressure feed carusual menuel- The normal llOW 0f liquid fuel 254 buretors, from reservoir 14 to nozzle 7 is controlled by a 80 An object of this invention is to provide a carmanually adjusted ValVe 13 Which regulates the buretor of the pressure-feed type wherein the norfree Opening thrOugh port 13. mal liquid fuel supply is temporarily augmented All tube 9 communicates thl'uugll en alf DeS- when the throttle is opened so as to still further SageWay 19 and metering restriCtiOn 19a With 'a Another object of this invention is to provide Cates through a compressed air supply pipe 21 5 a carburetor of the pressure-feed type wherein the With a Constant pressure air' pump (net shown). supply of additional 1iquid fuel for acceleration is A constant superatrnospherio air pressure is regulated in accordance with the temperature of maintained in IeseIVOiI 14 duringthe Operatien creases the acceleration fuel supply decreases. tiOn 22, Whieli admits COmDleSSed air lntO reser- Still another object of this invention is to provoir 14-from air passage 20, and a second smaller vide a carburetor of the pressure-feed type wheremetering restriction 23 which permits compressed in the acceleration device is combined with 'the air to escape from reservoir l4'into the atmosdevice for regulating the additional compressed phere at such a controlled rate as will maintain 95 air supply required, for compensation of the mixthe desired pressure in reservoir 14. ture delivered by the vmain jet. VIntegrally attached to the bottom wall of reser- With these and other objects in view which may voir 14 is a cylinder 24 which is divided by a be incident tomy improvements, my invention transverse wall 25 into an upper chamber 26 consists of the combination and-arrangementdof and a lower chamber 27. Chamber 26 communi- 100 elements hereinafter described and illustrated in categ through a pipe line 28, passageway 29 and the accompanying drawing which Figure l shows, port 30 with mixing chamber 4 and through a in central vertical section a carburetor embodyseries of ports 3l 'with reservoir 14. Adapted to ing my improvements. reciprocate within chamber 26, with an air-tight Figures 2 and 3 are fragmentary longitudinal fit, is a piston 32 having adjustably attached,105

sections of the acceleration pump looking in th thereto a piston rod 33 which passes through a directions of arrows2 andBrespectively. liquid-tight stuffing box 34 in wall 25 and is Referring to the drawing, the reference numeral similarly attached by screw threads to a second Ldenotes the body 'of a carburetor having a main piston 35 adapted to reciprocate in chamber 27 ne air intake 2,Venturtl1r0at 3,IniXiI1g Chamber f1, also with an air-tight fit. Interposed between 110 piston 32 and the top of chamber 26 is a helical spring 36 which is arranged to force piston 32 down in opposition to the action of the vacuum in mixing chamber 4 which is transmitted to chamber 26 through passage 29 and pipe 28.

Integrally attached to piston 35 is a sleeve valve 37 which is adapted toslidel in a valve chamber 38 integrally attached to the bottom wall of reservoir 14 and depending therefrom, as clearly-shown in the drawing.

Valve chamber 38 communicates with air passage 20 through a generally triangular shaped port 39 which admits compressed air into chamber 38 whenever valve 37 is raised and uncovers a part o f said port. The shape of port 39 is not truly triangular but the sides thereof are curved so that the area uncovered by'valve 37 at any given position is sufficient Vto pass the exact quantity of air required to forma mixture of de-. sired proportions, under the degree of vacuum existing in mixing chamber 4 at the time, as explained in my copending application, Serial No. 590,292 above referred to. Chamber 38 communicates with mixing chamber 4 by means of connecting passageways 40, 41, 42 and 43 and a slot-shaped port 44 in sleeve valve 37, the width of which port is equal to the diameter of passageway 40 which is also equal to that of passageway 20.

Chamber 27 communicates with liquid fuel tube 8 by means of a pipe line 45 and with reservoir 14 by means of exhaust port 46 and intake port 47, the former ybeing normally closed by a spring pressed check valve 48 which'is adjusted by a screw 49 threaded through a three-legged yoke 50 attached by screws 51 to the outside wall of cylinder 24. 'I'he legs of yoke 50 function as a guide for the ball 48. Port 47 is so positioned as to be normally closed by sleeve valve 37 and opened only when this valve is in its lowermost position. A small notch 52 is cut in the top edge of piston 35 which is arranged to register with port 46 when piston 35 is in its uppermost position and with port 47 when piston 35 is in its lowermost position, as clearly shown in the draw- Communication between chamber 27' and tube 8 through pipe line 45 is regulated by a valve 53 which is actuated by a thermostatic element 54 attached to pipe 45 and so calibrated as to raise valve 53 by a predetermined amount for each degree fall in temperature of the carburetor. Valve 53 is adjustably connected to thermostat 54 by a plurality of nuts which are threaded on valve stem 53 and embrace element 54.

With the arrangement just described it'is apparent that valve 53 is fully open only at the lowest working temperature of the carburetor and as this temperature rises valve 53 gradually restricts passageway 45 so that it is completely closed at the highest operating temperature of the carburetor. In this way the additional liquid fuel supplied for acceleration through pipe 45 is regulated in accordance with the temperature of the carburetor.

The operation of my device is as follows: When the engine is idling at its slowest speed the throttle is in its most restrictedposition, as shown in the drawing. In this position the clearance between the walls of the mixture outlet 5 and the throttle 6 is just sufcient to pass the amount of mixture required for idling. Under these circumstances the vacuum in mixing chamber 3 and chamber 26 is at a minimum, and spring 36 forces pistons 32 and 35 and sleeve valve .37 to their lowest positions, thus cutting off the auxiliary compressed air supply through passages 40, 41, 42, and 43 from passage 20. When piston 35 is in its lowest position, port 47 is opened and liquid fuel enters chamber 27 from reservoir 14, also all-liquid fuel is expelled from chamber- 26 through ports 31 into-reservoir 14.

As throttle 5 is opened there is an increase in vacuum in mixing chamber 4 and chamber 36 which draws pistons 32 and 35 and valve 37 up in proportion as this vacuum increases. As piston 35 ascends 'it compresses the liquid fuel in chamber 27 and forces it out through exhaust port 46 and pipe 45. The volume of liquid thus escaping from chamber 27 through these exits is inversely proportional to the resistances encountered in each, and as port 46 is a relatively larger, shorter andmore directpassage than pipe 45, its hydraulic resistance is very much less and a far greater volume of liquid normally escapes through port 46 as compared to pipe 45. The tension in the spring holding ball check valve 48 to its seat may be so adjusted by screw 49 as to make the resistance offered by the ball to the escape to liquid from chamber 27 negligible. In this case, the function of ball 50 is merely to prevent liquid fuel from entering chamber 27 through port 46. The area. of port 46 is made such that, when piston 35 is raisedV slowly, this port is sufficient to creased due to the reduction in the total area of discharge ports. This correspondingly slows up the travel of piston 35 on its vupward stroke and also the rate of opening of valve v39. This last prevents too sudden an increase in the air component during acceleration which is desirable when no acceleration fuel is supplied (valve 53 closed). But valvel 53 is only closed when the engine is at its highest working temperature, Aat which time acceleration is least difficult, provided the mixture is not impoverished by a sudden increase in the air component which is here prevented as just indicated above.

From the foregoing it is apparent stroke of piston 35 is regulated in accordance with the vacuum at port 30, so that as the vacuum increases the stroke of vpiston 35 increases and the amount of acceleration fuel supplied to the mixing chamber likewise increases in direct proportion. y

It is also apparent that since valve 37 and piston 35 move as a unit, as long as valve 53 is open, the supply of acceleration fuel to the mixing chamber is accompanied by a corresponding and proportionate supply of compressed air through air lines 20, 40, 41, 42 and 43.

Ports 31 in the walls' of chamber` 26 permit a free flow of liquid fuel into and out of chamber 26 whenever piston 32 reciprocates therein so that no resistance or retardation is offered to the movement ofpiston 32 except to steady it against vibrations due to minor fluctuations of vacuum in mixing chamber 4. i

As the throttle is closed, the vacuum in mixing chamber 4 decreases and spring 36 returns pistons 32 and 35 and valve 37 to the bottom of their that the strokes, thus cutting off the compressed air supply through passages 20, 40, 4l, 42 and 43 and permitting chamber 27 to refill with liquid fuel which enters from reservoir 14 through port 47 and from nozzle 6 through pipe 45 if valve 53 is open. The acceleration device is now ready for another cycle of operation.

Since valve 53 varies the opening in pipe 45 in accordance with the carburetor temperature it is obvious that the amount of acceleration fuel supplied to the mixing chamber is also regulated in accordance with temperature so that as the temperature rises the amount of acceleration fuel supplied diminishes, as required for best operating results.

If desired, the spring holding check valve 48 to its seat may be made of thermally sensitive metal so as to vary the resistance of the spring with change in temperature. By making the spring increase in strength with fall in temperature, a greater feed of acceleration fuel can be' forced out through pipe 45 at each stroke of piston 35 and also the duration of the acceleration fuel supply can be thus prolonged as the temp'erature falls. Also, if it is desired to increase the sensitiveness of the acceleration device and prolong its output, a weighted flap valve 55 can be hung in air intake passage 2 as shown on the drawing. When this is done, passage 2 is made square instead of circular in cross section so that valve 55 will lie flat against the top wall of passage 2 when fully open, so as not to restrict the opening through passage 2.

The force of gravity acting on valve 55- tends to keep it in a vertical (closed) position and the air drawn through passage 2 into mixing chamber 4 tends to swing the valve from its vertical position in accordance with the velocity of the air stream passing through passage 2, so that valve 55 assumes a horizontal position when the air passing through passage 2 reaches'its maximum velocity. But since valve 55 has an appreciable mass and inertia, it requires an appreciable time to move from its closed to open position., and during that interval of time, the vacuum in mixing chamber 4, due to the opening of throttle 5, is more slowly reduced by the retardation of the air stream through passage '2 due to the inertia of valve 55. The effect of valve 55 is therefore to temporarily increase and retard the decrease of vacuum in mixing chamber 4, whenever throttle 5 is opened and this in turn increases theforce and duration of the acceleration discharge.

From the foregoing disclosure it will be appreciated that I have not only produced a novel temperature controlled acceleration device for pressure feed carburetors, but have so combined this device with the auxiliary air valve as to coordinate its action therewith, and reduce the total mechanism required for these functions to a minimum.

While I have shown and described the pre-A ber liquid fuel under a continuous superatmos-,

pheric pressure and means responsive to the vacuum in said chamber for temporarily increasing said pressure when said throttle is opened, whereby said liquid fuel feed is temporarily increased at the same time.

3. In a carburetor having athrottle, a mixing chamber, means including a constant level fuel reservoir for supplying said chamber with liquid fuel under a continuous superatmospheric pressure, and temperature-regulated means within said reservoirl for temporarily increasing said liquid fuel supply when said throttle is opened.

' e. In a carburetor having a throttle, a mixing chamber, and means for feeding into said chamber liquid fuel under a continuous superatmospheric pressure, and vacuum controlled means for temporarily increasing said pressure when said throttle is opened, whereby said liquid fuel feed is temporarily increased at the same time, and a temperature responsive fuel valve for regulating said temporary increase of fuel feed in accordance with the temperature of the carburetor'.

5. In a carburetor having a throttle, a mixing chamber, means lfor supplying said chamber with liquid fuel and air, both under continuous superatmospheric pressures, and unitary automatic means for temporarily increasing said liquid fuel supply and increasing said air supply'when said throttle is opened.

v 6. In a carburetor having a throttle, a mixing chamber, means for supplying said chamber with -liquid fuel and air, both under continuous superatmospheric pressures, and unitary vacuumactuated means for temporarily increasing said liquid fuel supply and increasing said air supply when said throttle is opened.

7. In a carburetor having a. throttle, a mixing chamber, and means for feeding into said chamber liquid fuel and air, both under continuous superatmospheric pressures, and unitary automatic means for temporarily increasing said liquid fuel pressure and increasing said air supply when said throttle is opened.

8. In a carburetor having a throttle, a mixing chamber, an atomospheric air supply to said chamber, means for feeding compressed air to supply to said chamber liquid fuel under a continuous superatmospheric pressure, and automatic means for temporarily retarding said air supply and increasing the pressure on said liquid fuel when said throttle is opened, whereby said liquid fuel feed is temporarily increased at the same time.

9. In a carburetor having a throttle, a mixing chamber, means for supplying said chamber with atmospheric air and with liquid fuel under a continuous superatmospheric pressure, and means chamber, means for supplying said chamber with v liquid fuel and air, both under different continuous superatmospheric pressures, and unitary automatic means for temporarily increasing said liquid fuel supply and increasing said air supply.

when said throttle is opened;

\ ll. In a carburetor having a throttle, a mixing isov chamber, means for supplying said chamber with liquid fuel and air, both under different continuous superatmospheric pressures, and vacuumactuated means for temporarily increasing said liquid fuel supply and increasing said air supply when said throttle is opened.

12. In a carburetor having a throttle, a mixing chamber, means for supplying said chamber with liquid fuel under a continuous superatmospheric pressure, and vacuum-actuated temperatureregulated means for temporarily increasing said liquid fuel supply When said throttle is opened.

13. In a carburetor having a throttle, a mixing chamber, and means for feeding into said chamber liquid fuel and air both under continuous superatmospheric pressures and unitary automatic means for increasing said air feed and temporarily increasing said liquid fuel feed when said throttle is opened. Y

14. In a carburetor having a throttle, a mixing chamber, and means for feeding into said chamber liquid fuel under a continuous superatmospheric pressure and vacuum-controlled means for temporarily increasing said pressure when said throttle is opened, whereby said liquidfuel feed is temporarily increased at the same time, and means for regulating said temporary increase of fuel feed in accordance with the temperature of the carburetor.

15. In a carburetor having a throttle, a mixing chamber, means for supplying said chamber with liquid fuel and air under continuous superatmospheric pressures, and vacuum-controlled means for temporarily increasing said liquid fuel supply when said throttle is opened, and means for regulating said temporary increase of fuel supply in accordance with the temperature of the carburetor.

16. In a carburetor having a throttle, a mixing chamber, means for supplying said chamber with liquid fuel and air under a continuous superatmospheric pressure, and an acceleration device, subjected to said pressure, for temporarily increasing said liquid fuel supply when said throttle is opened.

17. In a carburetor having a throttle, a mixing chamber, and means for feeding into said chamber liquid fuel and air under a continuous superatmospheric pressure, and an acceleration device, subjected to said pressure, for temporarily increasing said pressure when said throttle is opened, whereby said liquid fuel and air feeds are temporarily increased at the same time.

y AUGUSTIN M. P REN'rIss. 

